آسیبهای چشمی فزاینده به دنبال تماس با پرتوهای لیزری، اپیدمی خاموش

نور یک محدوده قابل مشاهده و باریک از طیف الکترومغناطیسی است که مسئول بینایی میباشد، در حالی که لیزر (laser: light amplification by stimulated emission of radiation) یک پرتو تک رنگ و پلاریزه با فرکانسی مشخص و حداقل واگرایی از این طیف می باشد . از زمان اختراع لیزر در سال 1960، کاربرد آن در زندگی روزمره فراگیر شده و طی پیشرفتهای چشمگیر فناوری در دهه های گذشته، دستگاههای لیزر در کاربردهای بسیار متنوعی، از زمینه های آموزشی گرفته تا اهداف پزشکی، نظامی و آرایشی مورد استفاده قرار گرفته اند و حتی گاهاً به اشتباه توسط کودکان به عنوان اسباب بازی استفاده میشوند . نشانگرهای لیزری به عنوان دستگاههای کمانرژی شناخته می شوند که پرتوهای غیریونیزان کانونی ساطع میکنند که به طور گسترده در سالنهای سخنرانی برای ارائههای آموزشی- تجاری و حتی بعضاً در معابر و مراسمات با اهداف تبلیغاتی و زیبایی استفاده می شوند . این نشانگرها در انواع مختلف بر اساس طول موج پرتو نوری (و به تبع آن رنگ نور ساطع شده) وجود دارند که معمولاً لیزر قرمز (با طول موج 650-670 نانومتر) یا سبز (با طول موج 532 نانومتر) هستند (2). نشانگرهای لیزری با قدرت نور خروجی و طول موج کدگذاری می شوند.

increasing eye injuries following exposure to laser beams, the silent epidemic

while light is a visible and narrow range of the electromagnetic spectrum that is responsible for vision, light amplification by stimulated emission of radiation (laser) is a monochromatic and polarized beam with a specific frequency and minimum divergence from this spectrum (1). since the invention of the laser in 1960, its use has become widespread in everyday life. moreover, during the notable advances in technology in the past decades, laser devices have been used in a wide variety of applications, from educational fields to medical, military, and cosmetic purposes, and sometimes even mistakenly used by children as toys (2). laser pointers are known as low-energy devices that emit focal non-ionizing beams that are widely used in lecture halls for educational-commercial presentations and even sometimes in passages and ceremonies for advertising and elegance purposes (1). these markers exist in different types based on the wavelength of the light beam, and consequently the color of the emitted light, which is usually red (650-670 nm) or green (532 nm) (2).laser pointers are coded by output light power and wavelength. in the latest updates, the international electrotechnical commission has classified laser devices into four categories based on maximum output power, where handheld laser pointers are usually classified as 2m or sometimes 3r (table 1) (3). according to this classification, 2m types are considered safe due to their low output power and highly divergent light beam, along with the protective effect of the blink reflex, which reduces the exposure time of the laser light with the internal structures of the eye. however, possible eye damage in class 3r is controversial, especially during accidental exposure or accompanied with the use of optical tools such as magnifying glasses, binoculars or telescopes (4), and long-term viewing and deliberate direct observation (5). so, there is the possibility of severe eye damage in both classes, which has been reported in previous studies (2, 6). the most common ocular structure involved in laser injuries is retina due to the following two reasons: 1) it is optically transparent and 2) the refractive power of the eye focuses the radiation on the retina. it should be noted that the energy of radiation rays on the retina is more than 105 times in the cornea (7), which can reach a million times in the presence of the previously mentioned optical tools (8). eye damage by laser devices depends on the wavelength, exposure time, characteristic of eye refraction, and laser-ocular tissue interaction. in general, laser-ocular tissue interaction has three mechanisms as follows (7): 1) thermal (photothermal): the laser energy absorbed by the pigments causes an increase in the local temperature and coagulation of tissue proteins, and finally cell death and scar formation; 2) mechanical: laser energy is quickly absorbed in a very short period, and this sudden increase in temperature causes the liquid to evaporate, followed by the creation of a mechanical wave; and 3) chemical (photochemical): tissue chemical reactions caused by laser energy without a substantial increase in temperature. in this context, thermal damage is considered the most important mechanism in laser damage, which mainly occurs in short-wavelength lasers (i.e., green laser). in these injuries, retinal pigments act as mediators in the laser phototoxicity (4). so far, many reports have mentioned a wide range of damaging effects of lasers on the retina, including retinal holes (9), retinal hemorrhage (2), choroidal neovascularization (cnv) (10,11), photoreceptors damage (6), etc. nowadays, retinal damage caused by laser pointers is a matter of concern due to such factors as easy availability, cheap price, and widespread use (recreational and advertising use), as well as the lifelong visual disability that often affects children and young people, as active people in the suffered